EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

III-nitride semiconductor heterostructures have concentrated significant interest in the fields of optoelectronic and electronic devices. The introduction of Shockley partial dislocations, particularly in semipolar heterostructures due to strain relaxation, affects device performance. Such partials are referred to as a- or m-dislocations if their line is along <-1-120> or <1-100> directions respectively. The determination of their atomic core structures could elucidate their configurations in the material in the form of domains and loops, as well as their impact on material properties. Aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) is a powerful method to obtain such information. In this work emphasis was given on m-Shockley partials projected along <-1-120> directions for which their core structures can be evaluated directly under optimized imaging conditions. Molecular dynamics calculations using a Stillinger-Weber interatomic potential, and multislice HRTEM image simulations were employed. Energetically relaxed supercells of m-Shockley partials were properly rotated by 30° around [0001] considering crystallographic constraints. It was found that the projected core structures resemble significantly the structures of certain a-Shockley partials. HRTEM image simulations corresponding to imaging conditions able to resolve the Ga-N dumbbells were employed for the analysis of the relaxed supercells along <-1-120>. Similar contrast features were observed by comparing the resulting simulated HRTEM images to simulated images of a-Shockley partials under the same imaging conditions, rendering the two types of dislocations practically indistinguishable. As a result of this analysis, prominent structural units of the cores of a- and m-Shockley partial dislocations are indicated.

Supported by the State Scholarships Foundation (IKY) project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432) and the project HARMONIA UMO-2016/22/M/ST5/00298 funded by the Polish National Science Centre.